To the dismay of teenage girls everywhere, researchers who investigated a 2009 outbreak of E. coli that sprang from tubes of Nestlé’s Toll House raw cookie dough are advising people to bake their cookies before eating them.

What kid hasn’t fantasized about sending secret coded messages in invisible ink? Now a team of researchers from Tufts University has developed just such an encryption method using genetically engineered strains of E. coli bacteria.